X-Ray Topographic Investigation of Cellular Structure and its Relation to another Defects in Various Types of GaAs Single-Crystals

Abstract

The defect patterns in GaAs crystal grown using liquid encapsulated Czochralski and gradient freeze methods with various types of doping were characterized using complementary X-ray topographic methods. It was found that the cellular structure occurring in the 1ow doped crystal is developed independently from the actual growth surface. The occurrence of the cellular structure is connected with significant 1attice deformation, and some results point that significant stress can influence its formation. The high doping prevents formation of the cellular structure, but at higher doping the phenomenon of "cellular growth" can occur due to instabilities of the growth surface. The present results point that defect pattern in GaAs crystals is more affected by the type of doping than by the choice of the growth method.

Investigation of Misfit Dislocation Sources in GaAs Epitaxial Layers

“…It was found from the topographic investigation [5,9] that the substrates cut from the Czochralski-grown crystal still contain a considerable dislocation density in the outer part of the crystal, while it is lowered in the middle part of the crystals under 103 /cm2 . The dislocations form a system of glide bands.…”